The two campaigns locked in Minnesota's intensifying marriage amendment fight are wrestling with a glaring dividing line more stubborn than Democrat and Republican: Young versus old.

From California to Maine, an overriding thread that stitched together residents across the country is that younger voters tend to oppose the amendments and older voters generally support them.

"There's no question that's an accurate reflection of how people look at the issue," said Frank Schubert, a California-based consultant who is leading Minnesota for Marriage's effort to pass the measure.

Both campaigns are frantically trying to calibrate their strategies to build winning coalitions from their natural bases of support, but also broaden to groups that historically have embraced the other side.

In a move that attracted a younger audience, Minnesota for Marriage created the "She Said Yes" proposal contest at local fairs and plans to bring its message to college campuses around the state. Amendment opponents got "A Prairie Home Companion" radio host Garrison Keillor to record voice-mail greetings for new donors, which appealed to older voters. They're also using younger Minnesotans to persuade older family members to reject the measure.

In what is shaping up as a breathtakingly close race, these efforts could make all the difference.

The marriage amendment is blossoming into the most expensive campaign of the election season. The state already has laws banning same-sex marriage. Amendment supporters, perhaps mindful of a generational shift, want to cement it into the state's Constitution to prevent judges or future legislators from changing the law. If it passes, only another amendment to repeal could take it out.

The generational divide flared vividly nearly two weeks ago, when Minnesota Vikings punter Chris Kluwe published a scorching letter on the website Deadspin, lambasting a Maryland state legislator who criticized a Baltimore Ravens player's vocal support of gay marriage.

"Your vitriolic hatred and bigotry make me ashamed and disgusted to think that you are in any way responsible for shaping policy at any level," he wrote, in a letter that received national attention.

Minnesotans United for All Families, the group trying to defeat the marriage amendment, has built a high-energy coalition of young Democrats and Republicans. Many never knew talk show host Ellen DeGeneres before she came out as gay. They don't flinch at the same-sex flirtation at the end of the hit summer pop song, "Call Me Maybe."

"I really see this as the fight of my generation," said Elizabeth Minneman, 19, former chairwoman of the Minnesota Teenage Republicans.

Minneman and other young people say future generations eventually will look at same-sex marriage opposition the same way most Americans look back at interracial marriage. And they don't want to be on the wrong side of history.

"One day, once my generation comes into political power, we will look back and think it was silly this was ever on the ballot," Minneman said.

Several young conservatives said they reject the argument of amendment supporters that gay marriage threatens the institution or their own relationships. They also find it galling that marriage amendment supporters are trying to change the state Constitution potentially forever, limiting their ability to have a say if Minnesotans' feelings about same-sex marriage change in coming decades.

"They want to destroy people's ability to be happy together," said Kate Murray, 25, a Republican who calls herself a huge supporter of Republican presidential candidate Mitt Romney. "Frankly, who you want to marry is irrelevant to me, because I just want a job and a career and a chance to start a family."

Older voters' preference

Schubert and other marriage amendment supporters say there is no proof that younger people will hold these views as they get older. As young people age, marry and have families of their own, they begin to see marriage as a complex relationship, "not just a bumper sticker slogan," he said. When California voters passed a similar measure in 2008, 61 percent of voters older than 65 supported the amendment. So far, an unbroken string of 30 states have passed a similar marriage amendment. This summer, North Carolina voters -- from all age groups -- overwhelmingly approved a marriage amendment.

Several older Minnesotans -- Republicans and Democrats -- said they will be voting for the amendment. They say they are tired of seeing the media and pop culture desensitizing young people to what they say are the perils of same-sex relationships and marriage.

"There are two sides to this and the media is only showing one," said Leroy Fickert, a 64-year-old retiree from Dodge Center who has supported a mix of Democratic and Republican candidates. "But a traditional family, one man and one woman, is the best chance kids have. We are supposed to love each other, but when it comes to any sort of sexual intimacy between two people of the same sex, it is a sin."

Several older Minnesotans said they frequently spar their with children and grandchildren over the issue. Others say they just sit quiet, vowing to leave their mark in the voting booth.

"I think marriage is a union that is similar to Christ and his church," said Lorraine Ryberg, a 77-year-old retiree from Rochester. "Families are made of a husband and wife, children and grandchildren."

Gay rights advocates see a tidal change coming on the marriage issue, with young people of all political stripes on the leading edge. Minnesota, they say, could finally be the tipping point.

"If you are younger, like in your twenties, you are much more likely to know a gay person, someone who is open about their orientation, whether from school or even from TV," said Richard Socarides, a lawyer and national gay rights activist. "If you know someone, even if it's just from watching 'Glee,' it's much harder to justify discrimination against them because they are no longer an abstract concept but an actual person. You see that they are just like you."

Marriage amendment supporters are not convinced. Most polls in Minnesota show it passing, or within a whisker of passage.

"The entire argument that 'things are changing' depends on 19-year-olds holding their views throughout their lifetime, but the data suggests they won't," Schubert said. "Same-sex marriage is a very new phenomenon, less than 10 years old. We don't know how people are going react to this view over a long period of time."

Gunnar Birkerts, an internationally acclaimed modernist architect who designed buildings including the Federal Reserve Bank in Minneapolis, the Corning Museum of Glass in Corning, New York, and the University of Michigan Law Library, has died. He was 92.